Ferrite composition and electronic component

ABSTRACT

A ferrite composition comprises a main component and a sub component. The main component is comprised of 25.0 to 49.8 mol % iron oxide in terms of Fe 2 O 3 , 5.0 to 14.0 mol % copper oxide in terms of CuO, 0 to 40.0 mol % zinc oxide in terms of ZnO, and a remaining part of nickel oxide. The sub component includes 0.2 to 5.0 wt % silicon oxide in terms of SiO 2 , 0.10 to 3.00 wt % bismuth oxide in terms of Bi 2 O 3 , and 0.10 to 3.00 wt % cobalt oxide in terms of Co 3 O 4 , with respect to the main component.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ferrite composition suitable formanufacture of multilayer inductors for example and an electroniccomponent having a ferrite sintered body composed of the composition.

2. Description of the Related Art

Development of mobile devices such as smart phones with high performanceis remarkably advancing. In recent years, NFC (Near field communication)and non-contact power supply etc. are being adopted, and circuitsflowing higher AC currents than those of conventional ones areincreasing.

Also, due to response to high densification of electronic components,downsizing of the components is still strongly requested. Generally,with respect to inductance elements, Q values tend to decrease when ACcurrents increase or they are downsized. For such circumstances,magnetic core materials enabling high Q values even under increase of ACcurrent values or downsizing thereof are required as well as inductanceelements using the materials.

Note that, Patent Document 1 discloses magnetic materials havingexcellent anti-stress characteristic by adding SiO₂ and CoO to NiCuZnferrites. However, the magnetic materials of Patent Document 1 arematerials which are sintered 1050° C. or higher. Further, PatentDocument 1 does not disclose Q values under high amplitude currents.

Also, Patent Document 2 discloses ferrite materials having a smallmagnetic loss even under high amplitude currents by adding cobalt oxideto NiCuZn ferrites. However, in recent years, ferrite materials havinghigher performance than the ferrite materials disclosed in PatentDocument 2 are being requested.

Further, in multilayer inductors, coil conductors and ferrite layers arerequired to be fired integrally. Thus, ferrite compositions for themultilayer inductors are required to have a sintering temperature whichis the same or lower than the melting point of the coil conductors.

[Patent Document 1] JP Patent Application Laid Open No. H02-137301

[Patent Document 2] JP Patent Application Laid Open No. 2013-060332

SUMMARY OF THE INVENTION

Therefore, the present invention was made considering the abovesituations; and its object is to provide a ferrite composition enablinglow temperature sintering and having high Q values under high magneticfields and a small deterioration in the Q values under high amplitudecurrents and to provide an electronic component enabling downsizing.

In order to achieve such object, a ferrite composition according to thepresent invention comprises a main component and a sub component,wherein

said main component is comprised of 25.0 to 49.8 mol % iron oxide interms of Fe₂O₃, 5.0 to 14.0 mol % copper oxide in terms of CuO, 0 to40.0 mol % zinc oxide in terms of ZnO, and a remaining part of nickeloxide, and

said sub component includes 0.2 to 5.0 wt % silicon oxide in terms ofSiO₂, 0.10 to 3.00 wt % bismuth oxide in terms of Bi₂O₃, and 0.10 to3.00 wt % cobalt oxide in terms of Co₃O₄, with respect to the maincomponent 100 wt %.

An electronic component according to the present invention comprises aferrite sintered body composed of the above ferrite composition.

In the ferrite composition according to the present invention, thecontents of the oxides comprising the main component are set in theabove range, and further silicon oxide, bismuth oxide, and cobalt oxideare included in the above range as the sub component, which enables lowtemperature sintering. For example, the ferrite composition can besintered at about 900° C., which is lower than the melting point of Agavailable for inner electrodes. Also, the ferrite sintered body composedof the ferrite composition according to the present invention has asmall lowering rate of Q even if an exterior magnetic field isincreased, Q values larger than those of the conventional one, and smalldeterioration in the Q values under high amplitude currents.

Further, the ferrite sintered body composed of the ferrite compositionaccording to the present invention can increase Q values even undermagnetic fields higher than conventional ones. That is, for example,even under high external magnetic fields (tens to hundreds A/m) comparedwith conventional external magnetic fields (1 to 2 A/m), sufficientlyhigh Q values are maintained. Therefore, the electronic componentsaccording to the present invention can be used for large amplitudesignals compared with electronic components having ferrite sinteredbodies composed of the conventional ferrite compositions.

Also, the ferrite sintered body composed of the ferrite compositionsaccording to the present invention has a low loss and high Q values evenif AC currents higher than conventional ones are applied. Therefore, byusing the ferrite compositions according to the present invention,ferrite layers can be thinned and electronic components can bedownsized.

It is considered that the reason why such effects can be obtained iscomposite effects obtained by setting the main component in thepredetermined range and further setting each content of the subcomponent in a specific range.

Note that, the ferrite sintered body composed of the ferritecompositions according to the present invention is preferable for suchas multilayer inductors, multilayer L-C filters, multilayer common modefilters, and composite electronic components made by multilayer methodsor so. For example, the ferrite sintered body is also preferably usedfor LC composite electronic components and NFC coils etc. In particular,when μ is 80 or less, the ferrite sintered body is preferably used forusage of the NFC coils (e.g. 13.56 MHz) used in high frequency bands,high-frequency multilayer power inductors (e.g. 20 to 200 MHz), ormultilayer beads etc., for example. Also, when μ is more than 80, theferrite sintered body is preferably used for usage of multilayer powerinductors (e.g. 1 to 20 MHz) or small signal inductors etc.

The ferrite sintered body composed of the ferrite compositions accordingto the present invention has a small lowering rate of Q even if theexterior magnetic field is increased and large Q values. Since theferrite sintered body composed of such ferrite compositions has nodeterioration in characteristic under a large amplitude signal,electronic components can be downsized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a multilayer inductor according toone embodiment of the present invention.

FIG. 2 is a cross-sectional view of a LC composite electronic componentaccording to one embodiment of the present invention.

FIG. 3 is a graph showing a relation between μ and Q of each sample inan external magnetic field H=100 A/m.

FIG. 4 is a graph showing a relation between μ and Q of each sample inan external magnetic field H=200 A/m.

FIG. 5 is a graph showing variations of Q of each sample when anexternal magnetic field H varies.

FIG. 6A to FIG. 6C are photographs showing concentration distributionsregarding each of Bi, Si, and Co when the ferrite materials according tothe example of the present invention are structurally analyzed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described based onembodiments shown in the drawings.

As shown in FIG. 1, a multilayer inductor 1 according to one embodimentof the present invention has an element 2 and terminal electrodes 3. Theelement 2 is obtained by firing a green multilayer body in which coilconductors 5 are formed three-dimensionally and spirally via ferritelayers 4. The ferrite layers 4 are composed of a ferrite compositionaccording to one embodiment of the present invention. The multilayerinductor 1 is obtained by forming the terminal electrodes 3 at bothsides of the element 2 to connect the terminal electrodes 3 with leadingelectrodes 5 a and 5 b. A shape of the element 2 is not particularlylimited, but it is usually rectangular parallelepiped one. Also, thesize thereof is not particularly limited, either. A proper size can beadopted based on usage.

Materials of the coil conductors 5 and the leading electrodes 5 a and 5b are not particularly limited, and Ag, Cu, Au, Al, Pd, or Pd/Ag alloyetc. is used. Note that, Ti compound, Zr compound, or Si compound etc.may be added.

The ferrite composition according to the present embodiment is Ni—Cuferrite or Ni—Cu—Zn ferrite. The main component thereof may include ironoxide, copper oxide, and nickel oxide, or may further include zincoxide.

In the main component 100 mol %, in terms of Fe₂O₃, a content of ironoxide is 25.0 to 49.8 mol %, preferably 30.0 to 48.0 mol %, and morepreferably 34.0 to 48.0 mol %. When the content of iron oxide is toolarge or too small, sinterability deteriorates and, in particular,sintered density after low temperature sintering tends to decrease.

In the main component 100 mol %, in terms of CuO, a content of copperoxide is 5.0 to 14.0 mol %, preferably 7.0 to 12.0 mol %, and morepreferably 7.0 to 11.0 mol %. When the content of copper oxide is toosmall, sinterability deteriorates and, in particular, sintered densityafter low temperature sintering tends to decrease. When the content ofcopper oxide is too large, Q value tends to decrease.

In the main component 100 mol %, in terms of ZnO, a content of zincoxide is 0 to 40.0 mol %. That is, zinc oxide may not be included as themain component. When zinc oxide is included as the main component, thecontent of zinc oxide is preferably 0.5 to 32.0 mol % and morepreferably 1.0 to 30.0 mol %. When the content of zinc oxide is toolarge, Curie temperature tends to decrease.

A remaining part of the main component is comprised of nickel oxide.

In addition to the above main component, the ferrite compositionaccording to the present embodiment includes a sub component such assilicon oxide, bismuth oxide, and cobalt oxide.

With respect to the main component 100 wt %, in terms of SiO₂, a contentof silicon oxide is 0.2 to 5.0 wt %, preferably 0.25 wt % to 4.0 wt %,and more preferably 0.5 to 4.0 wt %. When the content of silicon oxideis too small, Q value tends to decrease and a lowering rate of Q tendsto increase. When the content of silicon oxide is too large,sinterability deteriorates and, in particular, sintered density afterlow temperature sintering tends to decrease.

With respect to the main component 100 wt %, in terms of Bi₂O₃, acontent of bismuth oxide is 0.10 to 3.00 wt % and preferably 0.20 to2.00 wt %. When the content of bismuth oxide is too small, sinterabilitydeteriorates and, in particular, sintered density after low temperaturesintering tends to decrease. When the content of bismuth oxide is toolarge, Q value tends to decrease and a lowering rate of Q tends toincrease.

With respect to the main component 100 wt %, in terms of Co₃O₄, acontent of cobalt oxide is 0.10 to 3.00 wt % and preferably 0.20 to 2.00wt %. When the content of cobalt oxide is too small, Q value tends todecrease and a lowering rate of Q tends to increase. When the content ofcobalt oxide is too large, sinterability deteriorates and, inparticular, sintered density after low temperature sintering tends todecrease.

In the ferrite composition according to the present embodiment, inaddition that a composition range of the main component is controlled inthe above range, the above silicon oxide, bismuth oxide, and cobaltoxide are always included as the sub component. As a result, it ispossible to decrease sintering temperature and use a metal such as Aghaving a relatively low melting point as an integrally fired innerconductor. Further, a ferrite sintered body sintered at low temperaturehas a small lowering rate of Q value and maintains a characteristicwhere Q value is high.

Note that, with respect to silicon oxide, bismuth oxide, and cobaltoxide, when any one or more thereof is not included, the above effectscannot be obtained adequately. That is, it is considered that the aboveeffects are composite effects which can be obtained only when siliconoxide, bismuth oxide, and cobalt oxide are included by a certain amountat the same time.

Also, in the ferrite composition according to the present embodiment, inaddition to the above sub component, additional components such asmanganese oxide like Mn₃O₄, zirconium oxide, and glass compound may befurther included in a range where the effects of the present inventionare not disturbed. A content of the additional components is notparticularly limited, and it is approximately 0.05 to 1.0 wt %, forexample.

Further, the ferrite composition according to the present embodiment mayinclude an oxide of inevitable impurity element.

Specifically, as the inevitable impurity element, C, S, Cl, As, Se, Br,Te and I, a typical metal element such as Li, Na, Mg, Al, Ca, Ga, Ge,Sr, Cd, In, Sb, Ba and Pb, and a transition metal element such as Sc,Ti, V, Cr, Y, Nb, Mo, Pd, Ag, Hf and Ta are exemplified. Also, the oxideof the inevitable impurity element may be included in the ferritecomposition as far as the content thereof is approximately 0.05 wt % orless.

The ferrite composition according to the present embodiment has ferriteparticles and crystal grain boundaries present among adjacent crystalparticles. An average crystal particle diameter of the crystal particlesis preferably 0.2 to 1.5 μm.

Next, an example of a method for manufacturing the ferrite compositionaccording to the present embodiment will be described. First, startingmaterials (a material of the main component and a material of the subcomponent) are mixed after they are weighted so as to satisfy apredetermined composition ratio, and a raw material mixture is obtained.As a mixing method, for example, wet mixing using a ball mill and drymixing using a dry mixer can be raised. Note that, it is preferable touse a starting material having an average particle diameter of 0.05 to1.0 μm.

As a material of the main component, iron oxide (α-Fe₂O₃), copper oxide(CuO), nickel oxide (NiO), zinc oxide (ZnO) if necessary, or compositeoxide etc. can be used. Further, other various compounds to become theabove oxides and composite oxides after firing can be used. As examplesto become the above oxides after firing, a metal alone, carbonate,oxalate, nitrate, hydroxide, halogenide, and organometallic compoundetc. can be exemplified.

As a material of the sub component, silicon oxide, bismuth oxide, andcobalt oxide can be used. The oxide to become the material of the subcomponent is not particularly limited, and a composite oxide or so canbe used. Further, other various compounds to become the above oxides andcomposite oxides after firing can be used. As examples to become theabove oxides after firing, a metal alone, carbonate, oxalate, nitrate,hydroxide, halogenide, and organometallic compound etc. can beexemplified.

Note that, Co₃O₄, which is an example of cobalt oxide, is preferable asa material of cobalt oxide. This is because it is easy to store andhandle and valence thereof is stable even in the air.

Next, the raw material mixture is calcined and a calcined material isobtained. Calcination is performed so as to induce thermal decompositionof the raw material, homogeneity of components, generation of theferrite, disappearance of ultrafine powder by sintering, and particlegrowth to a proper particle size and to convert the raw material mixtureto a form suitable for the following process. Such a calcination ispreferably performed at a temperature of 650 to 750° C. for 2 to 15hours in general. Calcination is usually performed under the atmosphere(air), but it may be performed under an atmosphere where an oxygenpartial pressure is lower than that of the atmosphere. Note that, themixing of the material of the main component and the material of the subcomponent may be performed before the calcination or after it.

Next, the calcined material is pulverized to obtain a pulverizedmaterial. Pulverization is performed to disconnect an aggregation sothat the calcined material becomes powders having a propersinterability. When the calcined material forms large lumps, wetpulverization is performed by using a ball mill or an attritor etc.after performing coarse pulverization. The wet pulverization isperformed until an average particle diameter of the pulverized materialbecomes preferably 0.1 to 1.0 μm or so.

By using the obtained pulverized material, a multilayer inductoraccording to the present embodiment is manufactured. A method formanufacturing the multilayer inductor is not limited, but hereinafter, asheet method is used.

First, the obtained pulverized material is slurried with an additivesuch as solvent and binder, and a paste is produced. Then, green sheetsare formed by using the paste. Next, through transforming the formedgreen sheets to a predetermined shape and performing a debinding stepand a firing step, the multilayer inductor according to the presentembodiment is obtained. The firing is performed at a temperature whichis the same or lower than the melting point of the coil conductor 5 andthe leading electrodes 5 a and 5 b. For example, when the coil conductor5 and the leading electrodes 5 a and 5 b are Ag (melting point: 962°C.), the firing is preferably performed at 850 to 920° C. The firing isusually performed for 1 to 5 hours or so. Also, the firing may beperformed in the atmosphere (air) or may be performed under anatmosphere where an oxygen partial pressure is lower than that of theatmosphere. The multilayer inductor obtained as this way is comprised ofthe ferrite composition according to the present embodiment.

Up to here, the embodiment of the present invention was described, butthe present invention is not limited to the embodiment. Needless to say,the present invention can be performed by various embodiments in a rangewhere the points of the present invention are not deviated. For example,as the ferrite layers 4 of the LC composite electronic component 10shown in FIG. 2, the ferrite composition of the present invention may beused. Note that, in FIG. 2, a part shown by sign 12 is an inductor part,and a part shown by sign 14 is a capacitor part.

Hereinafter, the present invention will be described based on moredetailed examples, but the present invention is not limited to theexamples.

Example 1

First, as materials of the main component, Fe₂O₃, NiO, CuO, and ZuO(when zinc oxide was included) were prepared. As materials of the subcomponent, SiO₂, Bi₂O₃, and Co₃O₄ were prepared.

Next, after powders of the prepared main component and sub componentwere weighted so that they satisfied the composition described in Tables1 and 2 as sintered bodies, they were wet mixed for 16 hours in a ballmill, and a raw material mixture was obtained.

Next, after the obtained raw material mixture was dried, it was calcinedfor 4 hours at 720° C. in the air, and the calcined powders wereobtained. The pulverized powders were obtained by wet pulverizing thecalcined powders for 72 hours in a steel ball mill.

Next, after drying the pulverized powders, granulation was performed byadding 10.0 wt % of a polyvinyl alcohol solution as a binder having 6 wt% concentration into the pulverized powder 100 wt % so as to obtaingranules. The granules were molded by pressure so as to satisfy amolding density of 3.20 Mg/m³, and toroidal-shaped (size=outer diameter13 mm×inner diameter 6 mm×height 3 mm) molded bodies were obtained.

Next, each of the molded bodies were fired for 2 hours at 900° C., whichis below the melting point of Ag (962° C.), in the air. Then, toroidalcore samples as sintered bodies were obtained. Further, the followingcharacteristic evaluations were performed on the samples.

Sintered Density

With respect to the obtained toroidal core samples, a sintered densitywas calculated from a size and weight of the sintered body after firing.In the present example, a sintered density of 5.0 Mg/m³ or more wasconsidered as good. Also, with respect to samples having a sintereddensity of less than 5.0 Mg/m³, the following characteristic evaluationswere omitted because other characteristic evaluations were considered asnot worthy of being performed.

Curie Temperature

A curie temperature was measured based on JIS-C-2560-1. In the presentexample, the evaluations were performed by whether the Curie temperaturewas 125° C. or higher. With respect to samples whose Curie temperaturewas less than 125° C., the following characteristic evaluations wereomitted because other characteristic evaluations were considered as notworthy of being performed due to inconvenience in an operatingtemperature of the inductor.

Permeability μ, Q Value and Lowering Rate of Q

With respect to samples having good sintered density and Curietemperature, primary and secondary sides thereof were wound by copperwires with 20 turns and 7 turns, respectively. Permeability μ and Qvalues were measured by using B-H Analyzer (IWATSU TEST INSTRUMENTSCORPORATION, B-H ANALYZER SY-8218) and AMPLIFIER (NF CORPORATION, HIGHSPEED BIPORLAR AMPLIFIER HSA 4101-IW). As the measuring conditions,measuring frequency was 1 MHz, measuring temperature was 25° C., andexternal magnetic fields were applied by 100 A/m and 200 A/m. Further,from the measured Q values, lowering rates of Q were calculated when theexterior magnetic field was increased from 100 A/m to 200 A/m.

In the present example, it is preferable that the lowering rate of Q is45% or lower when the exterior magnetic field was increased from 100 A/mto 200 A/m. Further, it is preferable that Q value is 120 or higher whenthe external magnetic field is 100 A/m and μ is 80 or smaller. Further,when the external magnetic field is 200 A/m and μ is 80 or smaller, Qvalue is preferably 100 or larger. The above results are shown in Table1 (Example) and Table 2 (Comparative Example). Also, samples where cellsof Curie temperature show ◯ represent that Curie temperature is 125° C.or higher, and the sample where a cell of Curie temperature shows xrepresents that Curie temperature is less than 125° C.

TABLE 1 Sintered Main Component Sub Component Density Lowering Sample(mol %) (wt %) (Mg/m³) Curie μ at Q at μ at Q at Rate of Q Number Fe₂O₃CuO ZnO SiO₂ Bi₂O₃ Co₃O₄ 900° C. Temperature 100 A/m 100 A/m 200 A/m 200A/m %  1 47.0 9.0 24.0 0.3 0.10 0.30 5.25 ◯ 148 47 158 31 33  2 47.0 9.024.0 0.2 0.20 0.50 5.26 ◯ 139 53 145 43 19  3 47.0 9.0 24.0 0.5 0.300.15 5.27 ◯ 125 80 140 45 44  4 47.0 9.0 30.0 1.0 0.30 0.24 5.27 ◯ 13888 144 55 38  5 47.0 9.0 26.0 1.4 0.50 0.20 5.18 ◯ 93 129 96 70 45  649.0 11.0 20.0 1.6 0.50 0.20 5.19 ◯ 66 125 67 103 18  7 47.0 9.0 24.01.8 0.20 0.20 5.08 ◯ 46 138 47 103 25  8 47.0 9.0 24.0 1.8 0.30 0.255.14 ◯ 47 154 49 116 24  9 47.0 9.0 24.0 2.5 3.00 1.50 5.23 ◯ 28 164 28143 13 10 47.0 9.0 24.0 4.0 1.50 0.80 5.04 ◯ 12 148 12 139 6 11 47.0 9.024.0 5.0 1.50 0.15 5.12 ◯ 13 165 13 161 3 12 47.0 9.0 24.0 5.0 3.00 0.155.19 ◯ 11 153 11 150 2 21 47.0 9.0 24.0 1.8 0.30 0.10 5.23 ◯ 50 143 52124 14 22 47.0 9.0 24.0 1.6 1.50 2.00 5.22 ◯ 33 169 34 148 12 23 47.09.0 24.0 1.8 0.30 0.50 5.11 ◯ 44 167 46 143 14 24 47.0 9.0 24.0 1.8 0.300.85 5.12 ◯ 42 189 44 152 20 25 48.0 9.0 26.0 1.8 0.30 1.00 5.03 ◯ 59131 60 126 4 26 49.0 9.0 28.0 1.8 0.30 1.00 5.03 ◯ 79 148 80 117 20 2745.0 9.0 24.0 1.8 0.50 1.20 5.04 ◯ 38 175 40 140 20 28 45.0 9.0 24.0 1.80.50 1.60 5.03 ◯ 30 170 30 164 4 29 45.0 9.0 24.0 1.6 1.50 3.00 5.08 ◯28 134 28 105 22 31a 25.0 9.0 10.0 1.4 3.00 3.00 5.21 ◯ 2 149 2 143 431b 30.0 9.0 6.0 1.2 0.80 1.50 5.22 ◯ 8 149 8 128 14 31c 49.8 9.0 10.01.4 1.00 1.00 5.31 ◯ 16 160 16 157 2 31d 40.0 9.0 23.0 2.0 1.00 1.605.26 ◯ 11 153 11 131 14 31e 38.0 5.0 10.0 1.4 1.00 1.00 5.02 ◯ 12 147 13137 7 31f 32.0 12.0 6.0 1.2 0.80 1.50 5.18 ◯ 9 152 9 117 23 31g 34.014.0 10.0 1.4 1.00 1.00 5.21 ◯ 13 164 14 119 27 31h 34.0 9.0 0.0 1.41.00 1.00 5.23 ◯ 3 154 4 153 1 31i 32.0 9.0 0.5 1.2 0.80 1.50 5.25 ◯ 3162 3 159 2 31j 34.0 7.0 1.0 1.4 1.00 1.00 5.00 ◯ 4 185 5 179 3 31k 34.010.0 3.0 1.4 1.00 1.00 5.24 ◯ 7 179 8 153 14 31l 39.0 9.0 32.0 1.2 0.801.50 5.18 ◯ 15 162 15 128 21 31m 40.0 9.0 40.0 1.8 1.00 1.00 5.12 ◯ 18174 18 139 20

TABLE 2 Main Component Sub Component Sintered Sample (mol %) (wt %)Density Curie μ at Q at μ at Q at Lowering Number Fe₂O₃ CuO ZnO SiO₂Bi₂O₃ Co₃O₄ 900° C. Temperature 100 A/m 100 A/m 200 A/m 200 A/m Rate ofQ % 41 48.0 8.0 3.0 0.0 0.00 0.00 5.28 ◯ 29 47 30 25 46 42 47.0 8.0 7.00.0 0.00 1.00 5.12 ◯ 28 105  28 88 15 43 47.0 9.0 12.0 1.8 1.00 0.005.28 ◯ 28 62 29 38 40 51 47.0 9.0 22.0 0.1 0.30 0.30 5.24 ◯ 145  19 159  8 58 52 47.0 9.0 30.0 7.0 1.00 0.15 4.60 — — — — — — 53 47.0 9.0 24.01.0 0.05 0.15 4.80 — — — — — — 54 47.0 9.0 24.0 1.0 5.00 0.15 5.31 ◯ 8180 82 42 48 55 47.0 9.0 24.0 1.0 0.30 0.05 5.32 ◯ 106  42 112  18 57 5647.0 9.0 30.0 1.8 0.30 5.00 4.66 — — — — — — 61 20.0 9.0 10.0 1.8 2.003.00 4.63 — — — — — — 62 52.0 9.0 10.0 1.8 1.00 1.00 4.10 — — — — — — 6340.0 3.0 10.0 1.8 1.00 1.00 4.83 — — — — — — 64 40.0 17.0 10.0 1.8 1.001.00 5.00 ◯ 12 53 13 48  9 65 40.0 9.0 45.0 1.8 1.00 1.00 5.25 X — — — ——

From Table 1 and Table 2, it was confirmed that lowering rates of Q weregood when three kinds of SiO₂, Bi₂O₃ and Co₃O₄ as the sub component wereincluded, and when the contents of the main component and the subcomponent were in a range of the present invention (sample numbers: 1 to31). Further, with respect to samples whose μ was 80 or smaller, it wasconfirmed that Q values were 120 or larger under the external magneticfield of 100 A/m, and that Q values were 100 or larger under theexternal magnetic field of 200 A/m. On the other hand, when either themain component or the sub component was out of the range of the presentinvention (sample numbers: 41 to 65), sintered bodies whose any one ormore of sintered density, Curie temperature, lowering rate of Q, and Qvalue was out of the excellent range were obtained.

Further, FIG. 3 (H=100 A/m) and FIG. 4 (H=200 A/m) represent that theresults of Table 1 and Table 2 were graphed by every external magneticfield. According to FIG. 3 and FIG. 4, it is clear that Q values ofExample are higher than those of Comparative Example when samples ofExample and Comparative Example whose μ is close are compared.

Example 2

With respect to sample number 28 of Table 1 and sample numbers 41 to 43of Table 2, FIG. 5 was obtained by summarizing the results of Q valuesmeasured under an external magnetic field (H=20 to 400 A/m) except forH=100 A/m and H=200 A/m. Other factors other than the external magneticfield were measured in the same way as with Example 1. Note that, samplenumber 41 corresponds to a conventional non-additive material, samplenumber 42 corresponds to a conventional Co additive material, and samplenumber 43 corresponds to a conventional SiBi additive material.

From FIG. 5, it is understood that the SiCoBi additive materialaccording to the present invention has a small lowering rate of Q duringrising of the external magnetic field and can keep Q values high underthe high magnetic fields of 20 to 400 A/m compared with the conventionalnon-additive material, Co additive material, and SiBi additive material.

Example 3

With respect to sample number 37 of Table 1, a structural analysis wasperformed by a method of EDX elemental mapping by using STEM HITACHIUltra-thin Film Evaluation System HD-2000. The results were shown inFIG. 6A to FIG. 6C. FIG. 6A to FIG. 6C show concentration distributionsof Bi, Si, and CO, respectively. The white areas are whereconcentrations of each of the elements are relatively high.

As shown in FIG. 6A to FIG. 6C, Si and Bi are segregated to coverferrite particles in the ferrite materials according to the presentinvention. On the other hand, Co is comparatively uniformly present inthe ferrite materials by dissolving to the ferrite particles in solid.

The reason why Q values under large amplitude currents of the ferritematerials according to the present invention improve is not clear.However, a synergistic effect where Si and Bi are segregated at the samearea and Co is comparatively uniformly present is possibly considered asthe reason.

As the above, the ferrite material according to the present inventioncan be sintered at a temperature lower than the melting point of Ag(962° C.). Further, the sintered body obtained by sintering the ferritematerial according to the present invention at a low temperature has ahigh characteristic even under high electric currents. Therefore, byusing the ferrite material according to the present invention, it ispossible to obtain electronic components which can be downsized andfurther are effective for even large amplitude signals.

NUMERICAL REFERENCES

-   1 . . . multilayer inductor-   2 . . . element-   3 . . . terminal electrode-   4 . . . multilayer body-   5 . . . coil conductor-   5 a, 5 b . . . leading electrode-   10 . . . LC composite electronic component-   12 . . . inductor part-   14 . . . capacitor part

The invention claimed is:
 1. A ferrite composition comprising a maincomponent and a sub component, wherein said main component is comprisedof 25.0 to 45.0 mol % iron oxide in terms of Fe₂O₃, 7.0 to 11.0 mol %copper oxide in terms of CuO, 0 to 40.0 mol % zinc oxide in terms ofZnO, and a remaining part of nickel oxide, said sub component includes1.2 to 5.0 wt % silicon oxide in terms of SiO₂, 0.10 to 3.00 wt %bismuth oxide in terms of Bi₂O₃, and 0.10 to 3.00 wt % cobalt oxide interms of Co₃O₄, with respect to the main component 100 wt %, andpermeability μ is 80 or less.
 2. An electronic component comprising aferrite sintered body composed of the ferrite composition according toclaim
 1. 3. The ferrite composition according to claim 1, wherein cobaltoxide in terms of Co₃O₄ is present in the sub component in an amount of0.8 to 3.00 wt %.
 4. The ferrite composition according to claim 1,further comprising ferrite particles and crystal grain boundaries amongadjacent crystal particles, wherein an average crystal particle diameterof the crystal particles is 0.2 to 1.5 μm.
 5. The ferrite compositionaccording to claim 1, wherein bismuth oxide in terms of Bi₂O₃ is presentin the sub component in an amount of at least 0.20 wt %.
 6. A multilayerinductor comprising an element comprising: ferrite layers composed ofthe ferrite composition according to claim 1, and coil conductors madeof Ag and formed three-dimensionally and spirally via the ferritelayers.